This invention relates to an improved heating and cooling system which reduces the amount of electric energy used and therefore lowers operating costs.
The majority of new electric heating and cooling systems being installed today are air source heat pumps. The air source unit, in the heating mode, suffers from a number of problems whereby a significant amount of costly supplementary heat is required. These problems result from trying to extract heat from very cold outside air that often ranges from 40.degree. F. to -20.degree. F. By using water in the temperature range of 60.degree. F. to 40.degree. F., heated by the sun and stored in the earth, most if not all of the problems encountered by the air source system can be overcome. Water source heat pumps, wherein water temperatures are above 60.degree. F., have been used successfully in Southern States, particularly in Florida. Partly because of the previous low cost of energy and partly because of technological problems in operating water source heat pumps using water below 60.degree. F., there has been little or no use of ground water systems in the colder climates.
Recently several manufacturers have developed water source heat pumps for closed loop office building applications that will operate with water at such lower temperatures; however, there are implementation problems involved in adapting one of these units for use in a ground water application in small buildings. In northern climates, the winter heating load (i.e. BTU heat loss) capacity is two to four times greater than the average summer air conditioning load. The standard approach is to size either an air or water source heat pump based on the air conditioning load. This results in not enough heating capacity in the winter, which capacity must be made up by expensive supplemental electric or oil heat. The other choice is to size the system based on the larger heating load, but this results in poor humidity control because of short air conditioning cycles. Even with the present invention and its solution to the previously mentioned problems, it is not cost-effective to install extra heating or cooling capacity to handle the few days a year when extremely hot or cool weather is encountered. What is required in conjunction with a system that can be independently sized for heating and cooling is a low cost supplemental or backup heating and cooling means for extreme weather situations. It is one object of the present invention to provide such means.
Another object of this invention is to provide a very economical air conditioning system. In view of the fact that many utilities have a peak load in the summer due to peaks in air conditioning use, much higher prices are charged for electricity in the summer thereby making air conditioning costs about equal to heating costs even though far less energy is actually consumed during air conditioning.